Information storage medium, information recording method, and information recording/reproduction apparatus

ABSTRACT

This invention achieves high-density recording while preventing recording units from overlapping. Recording is done to form a gap between predetermined recording units. Since this gap is formed, even when a rotation driving mechanism of a medium suffers rotation nonuniformity, two neighboring recording units never overlap each other, and destruction of recording data can be prevented.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2001-143530, filed May 14,2001, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a high-density information recordingtechnique using a focused beam (blue laser or the like). Moreparticularly, the present invention relates to an improvement in aninformation recording method for a high-density optical disc on/fromwhich digital information is recorded/reproduced at constant linearvelocity (CLV). Also, the present invention relates to an inter-layercrosstalk reduction technique in a recordable optical disc having arecording multilayer including two or more layers per side.

2. Description of the Related Art

As a high-density information storage capable of repeated recording(repeated rewrite) using a focused beam, optical discs such as aDVD-RAM, DVD-RW, and the like is known.

<<Problem 1>>

In a DVD-RW (rewritable medium), new data is recorded by partiallyoverwriting an already data recorded portion (Restricted Overwrite). Inthis case, since already recorded data is partially destroyed to recordthe next data, the reliability of information recorded on an informationstorage medium suffers considerably.

<<Problem 2>>

On the other hand, a DVD-RAM (repeated recordable medium) suffers thefollowing problems:

a) Since data are recorded between neighboring ones of a large number ofprepit headers present on an information storage medium, the informationrecording efficiency (recording density) lowers, thus disturbing largecapacity.

b) When a two-recording layer structure per side is adopted for largecapacity, inter-layer crosstalk is generated due to prepit headers, thusdeteriorating reproduction signal characteristics. That is, in arecording layer, since recorded and unrecorded portions have a lightreflectance difference, inter-layer crosstalk in which thepresence/absence of recording marks on the other recording layerinfluences a reproduction signal is generated, thus deterioratingreproduction signal characteristics.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, predetermined recordingunits (e.g., 16 to 32 sectors/ECC blocks of 32 to 64 kbytes) arerecorded to have a gap (δ) therebetween. Since the gap (δ) is formed,even when a rotation driving mechanism (spindle motor) of a mediumsuffers rotation nonuniformity, neighboring recording units can beprevented from overlapping each other, thus preventing recorded datafrom being destroyed (due to some recording marks destroyed when theneighboring recording units overlap each other), and maintaining highreliability of recorded data.

According to another aspect of the present invention, in this inventionusing a one-sided, recording multilayer type disc-shaped medium (e.g.,one-sided, two-layered optical disc 9) which has spiral tracks withtrack pitch Pt, data recording is done via an objective lens havingnumerical aperture NA and an intermediate layer which has refractiveindex n and thickness t. This data recording is made to form a gap (δ)between predetermined recording units (ECC blocks). If D=2ttan{sin⁻¹(NA/n)}, length δ of the gap is given by “δ≦π(D+Pt)D/Pt”.

According to still another aspect of the present invention, uponsuccessively recording data for respective predetermined recording units(ECC blocks) along spiral tracks on a disc-shaped information storagemedium having a rotation center, a gap (δ) is formed between thepredetermined recording units (ECC blocks) along the tracks. In at leastone pair of neighboring tracks of the tracks, the angular position ofthe gap (δ) formed on one of the neighboring tracks with respect to therotation center is different from the angular position of the gap (δ)formed on the other one of the neighboring tracks with respect to therotation center.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a view for explaining a data recording method on aninformation storage medium (recordable optical disc using a blue laser)according to an embodiment of the present invention;

FIG. 2 is a view for explaining inter-layer crosstalk in the informationstorage medium (one-sided, two-layered type) according to the embodimentof the present invention;

FIG. 3 is a view for explaining the configuration of physical sectordata recorded on the information storage medium according to theembodiment of the present invention;

FIG. 4 is a view for explaining a method of forming an ECC block withrespect to physical sector data shown in FIG. 3;

FIG. 5 is a view for explaining the internal structure of an ECC blockrecorded on the information storage medium according to the embodimentof the present invention;

FIG. 6 is a block diagram for explaining the arrangement of aninformation recording/reproduction apparatus according to the embodimentof the present invention;

FIG. 7 is a flow chart for explaining the format sequence in the ECCblock structure in FIG. 4;

FIG. 8 is a view for explaining a data recording method on aninformation storage medium (recordable optical disc using a blue laser)according to another embodiment of the present invention;

FIG. 9 is a view for explaining necessity of a gap (groove gap) in theinformation storage medium according to the present invention;

FIG. 10 is a view for explaining a data recording method on aninformation storage medium (recordable optical disc using a blue laser)according to still another embodiment of the present invention;

FIG. 11 is a view for explaining the maximum allowable range of gaps(groove gaps) on the information storage medium according to the presentinvention;

FIG. 12 is a view for explaining an information storage medium formedwith a mark that determines a recording start position according tostill another embodiment of the present invention;

FIG. 13 is a flow chart for explaining a recording method or rewritemethod in the information recording/reproduction apparatus according tothe embodiment of the present invention; and

FIG. 14 is a flow chart for explaining a process for forming gap δ inthe recording method according to the embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

An information storage medium, information recording method, andinformation recording/reproduction apparatus according to variousembodiments of the present invention will be described hereinafter withreference to the accompanying drawings.

FIG. 1 is a view for explaining the basic concept of a data recordingmethod on information storage medium (recordable optical disc using ablue laser) 9 according to an embodiment of the present invention. FIG.2 schematically shows the structure of this information storage medium(one-sided, two-layered type) 9.

When information storage medium 9 in FIG. 1 is of one-sided, two-layeredtype shown in (a) of FIG. 2, for example, phase change type firstrecording layer 123 is formed on substrate 90 of medium 9, intermediatelayer 124 which has thickness t and refractive index n is formedthereon, phase change type 0th recording layer 122 is formed thereon,and transparent protection layer 125 (having a thickness of about 100μm) is formed thereon.

On information storage medium 9 shown in FIGS. 1 and 2, fine pre-groovesare spirally or concentrically formed as embossed patterns, and formtracks 112. By forming recording marks 127 (in (b) of FIG. 2) on therecording layer (122 or 123 in (a) of FIG. 2) along tracks 112,information is recorded.

In this embodiment, information is recorded or rewritten for respectivecontinuous data recording units (110 a, 110 b, and 110 c in FIG. 1)where recording marks 127 are continuously formed, thus formingrecording marks 127. In this case, gaps 111 b and 111 c with length δare formed between neighboring continuous data recording units 110 a,110 b, and 110 c. In this way, the gist of the data recording methodaccording to this embodiment resides in formation of predetermined gap δbetween neighboring data recording units.

When gaps 111 b and 111 c are formed between neighboring continuous datarecording units 110 a, 110 b, and 110 c, as shown in FIG. 1, these gaps(δ) absorb the influence (jitter) of rotation nonuniformity of a spindlemotor (204 in FIG. 6 to be described later) that rotates disc-shapedmedium 9. That is, since this gap (e.g., 111 b) is formed, even whenlarge jitter is produced due to rotation nonuniformity of a rotationdriving system upon information recording, an overlapping portion can beprevented from being formed between neighboring continuous datarecording units (e.g., 110 a and 110 b), and data in each continuousdata recording unit 110 can be stably and easily rewritten. This is alarge feature obtained by the data recording method that forms gap δbetween neighboring data recording units.

This embodiment adopts CLV (Constant Linear Velocity) recording in whichlength δ of each gap 111 and length L of each continuous data recordingunit 110 always become constant independently of the radial position ininformation storage medium 9. A data structure in continuous datarecording unit 110 is formed by recording synchronization VFO (VariableFrequency Oscillator) area 113 formed at the beginning of continuousdata recording unit 110, and recording area 114 which follows area 113.

Note that the contents of recorded information 114 in FIG. 1 areobtained by modulating and recording data of one whole ECC block (e.g.,data as a combination of small ECC block 8-0 in (f) of FIG. 4 to bedescribed later and small ECC block 8-1 in (g) of FIG. 4). However, thecontents upon practicing the present invention are not limited to thesecontents. For example, the practice contents of the present inventioninclude a case wherein recorded information 114 is made up of aplurality of ECC blocks or of a fraction of an integer of data in oneECC block. Alternatively, one recorded information 114 may be formed ofone or a plurality of pieces of physical sector information 4 shown inFIG. 3 (to be described later).

A great reduction effect of inter-layer crosstalk on one-sided,two-recording layer type information storage medium 9 by the recordingmethod in FIG. 1 will be explained below using FIG. 2.

For example, a case will be examined below wherein laser beam (itswavelength λ is around 405 nm) 120 is focused on first recording layer123 via objective lens 121 (its numerical aperture NA is, for example,around 0.85), and information recorded on first recording layer 123 isreproduced by detecting a change in amount of light reflected by firstrecording layer 123, as shown in (a) of FIG. 2. At this time, some lightcomponents of laser beam 120 are reflected by 0th recording layer 122,pass through objective lens 121 again, and leak into detection light.

As described above in <<Problem 2>> of the prior art, already recordedand unrecorded portions (inside and outside recording marks 127) inrecording layers 122 and 123 have a light reflectance difference.Therefore, the amount of light which is reflected by 0th recording layer122 and leaks into detection light changes considerably between a casewherein 0th recording layer 122 is completely unrecorded and has norecording marks 127, and a case wherein data have already been recordedon the entire surface of 0th recording layer 122 and recording marks 127are distributed everywhere. The change in amount of light which isreflected by 0th recording layer 122 and leaks into detection light isreflected by first recording layer 123 and leaks into a reproductionsignal used to reproduce information (inter-layer crosstalk), thusdeteriorating reproduction signal characteristics.

Let D be the diameter of laser beam 120 that strikes 0th recording layer122, NA be the numerical aperture of objective lens 121, n be therefractive index of intermediate layer 124, and t be the thickness ofintermediate layer 124 under the condition that the laser beam isfocused on first recording layer 123 shown in (a) of FIG. 2. Then,since:NA=n sin θ  (1)D=2t tan θ  (2)we haveD=2t tan{sin⁻¹(NA/n)}  (3)

A case will be examined below wherein a plurality of neighboring gaps111 align in the radial direction (perpendicular to tracks 112) ofoptical disc 9, as shown in (b) of FIG. 2.

If δ>D, laser beam 120 may completely fall within the region where theplurality of neighboring gaps 111 align (not shown). At this time, theregion of laser beam 120 with diameter D contains no recording marks 127at all, i.e., corresponds to an unrecorded state (which will be referredto as state a hereinafter for the sake of simplicity).

If laser beam 120 with diameter D has moved to a position largelyseparated from the region where gaps 111 align, the entire surfacewithin the region of laser beam 120 with diameter D is filled withrecording marks 127 (this state will be referred to as state ghereinafter).

As described above, since regions inside and outside each recording mark127 have a light reflectance difference, the amounts of laser beam 120reflected by 0th recording layer 122 in states a and g have a largedifference, and very large inter-layer crosstalk occurs consequently.

By contrast, if δ≦D, i.e., a state that satisfies:δ≦2t tan{sin⁻¹(NA/n)}  (4)is set, since the region where gaps 111 align is present only on aportion within the region of laser beam 120 with diameter D, a change inamount of laser beam 120 reflected by 0th recording layer 122 (i.e.,inter-layer crosstalk) when laser beam 120 passes by the region wheregaps 111 align becomes smaller than the difference between states α andβ described above.

In this manner, since gaps 111 b and 111 c are laid out betweenneighboring continuous recording units 110 a, 110 b, and 110 c, and gaps111 b and 111 c are set to have small length δ, an inter-layer crosstalkamount upon reproduction of one-sided, multi-layered disc can bereduced. A large characteristic feature of this embodiment lies in thispoint.

Note that the inter-layer crosstalk reduction effect appears remarkablywhen:δ≦D/2(i.e., δ≦t tan{sin⁻¹(NA/n)})   (5)

As a result of further tests and evaluations, when δ is limited to fallwithin the range:δ≦D/4(i.e., δ≦t tan{sin⁻¹(NA/n)}/2)   (6)a condition that suffers less characteristic deterioration of areproduction signal (suffers less influence of inter-layer crosstalk)can be obtained.

For example, when NA=0.85, n=1.57, and t=50 μm, gap δ is δ≦64 μm frominequality (4). On the other hand, δ<32 μm from inequality (5), and δ≦16μm from inequality (6).

As described above, in the embodiment of the present invention, data arerecorded along tracks by CLV. Hence, at a radial position where thelength per round of information storage medium 9 deviates from aninteger multiple of length L+δ (i.e., the physical periodic length ofgaps 111 which align at intervals in the direction along tracks 112),the positions of gaps 111 are different from each other betweenneighboring tracks.

By contrast, at a radial position where the length per round ofinformation storage medium 9 matches an integer multiple of length L+δ(physical periodic length of gaps 111), gaps 111 are arranged atneighboring positions between neighboring tracks, and gap regions 111align in the radial direction of information storage medium 9, as shownin (b) of FIG. 2. At such radial position, the physical periodic lengthof gaps 111 is changed in the direction along tracks 112 to lay out gaps111 at non-neighboring positions between neighboring tracks. Acharacteristic feature of the present invention also lies in this point.

FIG. 3 is a view for explaining the configuration of physical sectordata recorded on the information storage medium according to theembodiment of the present invention. FIG. 4 is a view for explaining amethod of forming an ECC block with respect to physical sector datashown in FIG. 3. The concept associated with the structure in an ECCblock in the embodiment of the present invention will be explained belowwith reference to FIGS. 3 and 4.

AV information and stream information, which are transferredcontinuously, are broken up into small pieces, which are converted intopack structures appended with pack headers, and these packs are recordedon information storage medium (optical disc) 9. That is, as shown in (a)of FIG. 3, video information and audio information are transferred whilebeing arranged along the time axis in the form of video packs 1-0, 1-1,1-2, . . . , and audio packs 2-0, 2-1, 2-2, . . . . Each of video packs1-0, . . . and audio packs 2-0, . . . has a data size of 2048 bytes,which match the logical sector information size. Video packs 1-0, . . .and audio packs 2-0, . . . are abstractly handled as a plurality ofpieces of logical sector information 3-1 to 3-31 in the logical layer,as shown in (b) of FIG. 3. (That is, examples of practical contents ofthe plurality of pieces of logical sector information 3-1 to 3-31correspond to video packs 1-0, . . . and audio packs 2-0, . . . )

In the embodiment shown in FIGS. 3 and 4, since physical sectorinformation and logical sector information match, these pieces ofinformation are handled as a plurality of pieces of physical sectorinformation 4-0 to 4-31, as shown in (c) of FIG. 3.

As will be described in detail later, each physical sector information(4-0 to 4-31) has the following configuration. That is, 4-byte PIDinformation, 2-byte IED information, and a 10-byte reserve field (thesize in an existing DVD is 6 bytes) are arranged at the head of eachinformation, and 4-byte EDC is arranged at the end of information (data0-0-0 to data 0-0-5). After that, that sequence is broken up into188-byte data (each of data 0-0-0 to data 0-0-5), error correction PI(inner-code parity) data (PIO-0-0 to PIO-0-5) are appended to every188-byte data, and these data are arranged in turn, as shown in (d) ofFIG. 3 or (d) of FIG. 4. In odd-numbered physical sector data (firstphysical sector data 5-0), PO (outer-code parity) data (P0) is arrangedat the end of data to complete physical sector data 5-0.

The embodiment of the present invention is characterized in thateven-numbered physical sector data (second physical sector data 5-1) hasa structure in which PO data (PO1) is arranged in the second column fromthe end of data, and data 1-1-5 and PI data (PI1-i-5) are arranged atthe end of the even-numbered physical sector data. Physical sector data5-0 to 5-31, which are completed in this manner, are recorded on anoptical disc (information storage medium 9) in accordance with the orderthey are arranged, as shown in (e) of FIG. 3.

As shown in (d), (f), and (g) of FIG. 4, one physical sector data 5-0 isformed as a combination of data in two different small ECC blocks 8-0and 8-1. (In this embodiment, ECC blocks 8-0 and 8-1 (small units) shownin (f) and (g) of FIG. 4 are called small ECC blocks, and a combinationof two small ECC blocks 8-0 and 8-1 as a whole is called a general ECCblock.) More specifically, data in physical sector data 5-0 is finelybroken up into 200-byte data, and 188-byte data 0-0-0 and PI data 0-0-0are arranged in the first row in ECC block 8-0. Next 188-byte data 0-1-0and PI 0-1-0 in physical sector data 5-0 are arranged in the first rowin small ECC block 8-1. Furthermore, next 188-byte data 0-0-1 and PIdata 0-0-1 are arranged on the second row in ECC block 8-0. Of PO datain small ECC block 8-1, first 200 bytes are inserted in the sixth row insmall ECC block 8-1 as P0. As a result, data from data 0-0-0 to PO0 formphysical sector data 5-0.

First data 1-0-0 and PI 1-0-0 that follows the first data in nextphysical sector data 5-1 are arranged in the seventh row in ECC block8-0, as shown in (f) of FIG. 4. Of PO data in ECC block 8-0, first200-byte data is arranged as P01 in the 12th row in ECC block 8-0.

In this way, PO data (PO, PO1) for respective rows (200 bytes) arearranged at equal intervals for respective physical sector data 5-0 to5-31, and their arrangement positions have a difference for one physicalsector data between a pair of small ECC blocks 8-0 and 8-1.

FIG. 5 is a view for explaining the internal structure of an ECC blockrecorded on the information storage medium according to the embodimentof the present invention. FIG. 5 exemplifies the detailed structure insmall ECC block 8-0 or 8-1 shown in (f) or (g) of FIG. 4. Note that thenumerals assigned to “sectors” in FIG. 5 indicate row numbers of datasectors.

The right side of FIG. 5 shows a combined state of two, right and left(for each 200-byte column) small ECC blocks. Each small ECC block has astructure in which 12-byte PI data is appended every 188 bytes, and POdata for 16 rows is appended. The PO data for 16 rows is decomposed intorow data, each of which is interleaved and inserted at every 12-rowpositions. A hatched portion of 200-byte columns per row in FIG. 5 meansinterleaved and inserted PO data.

The user information size assigned per sector is 2048 bytes as in anexisting DVD, and information having the same contents as those oflogical sector information recognized in the application layer is set aseach physical sector information (main data). Four-byte data IDinformation, 2-byte IED information, and 10-byte reserve field (the sizein an existing DVD is δ bytes) are arranged at the head of 2048 bytes ofthe main data (physical sector information), and 4-byte EDC data isarranged at the end of the main data, thus forming all data of aphysical sector.

Since one physical sector data is interleaved across two small ECCblocks (i.e., within a general ECC block), an error-correctable bursterror length can be improved to nearly twice that of the prior art. Thatis, one physical sector data is broken up into 188-byte data, each ofwhich forms one row data by appending 12-byte PI data (since theexisting PI size is 10 bytes, and is increased to 12 bytes, errorcorrection performance per row can be improved), and these row data arealternately and sequentially arranged in right and left different ECCblocks. This is also one of the characteristic features of thisembodiment.

Data (data sector) in one physical sector has an odd number of rows,i.e., 11 rows. This is also a characteristic feature of this embodiment.Since the data sector is made up of an odd number of rows, the totalnumber of rows can be even upon inserting one PO row in each physicalsector, and the PO row can be properly inserted in two small ECC blocks(i.e., one general ECC block) without forming any odd row.

PID information is always arranged at the head position (upper leftcorner position in FIG. 5) of each physical sector, and the PO insertpositions are devised to allow efficient interleave insertion of PO datain the embodiment shown in FIG. 5. That is, PO data is arranged at thelast row position of an even sector, and PO data is arranged at thesecond row position from the end of the sector in an odd sector. As aresult, PO data are arranged in a single ECC block, and all physicalsectors can have the same data size. This is also a characteristicfeature of this embodiment.

The arrangement of an information recording/reproduction apparatusaccording to the embodiment of the present invention will be describedbelow with reference to FIG. 6.

1. Function of Information Recording/Reproduction Unit

1-1. Basic Function of Information Recording/Reproduction Unit

An information recording/reproduction unit executes the followingprocesses are done. That is,

the unit records new information or rewrites (or erase) information at apredetermined position on information storage medium (optical disc) 9using a focused beam spot; and

the unit reproduces already recorded information from a predeterminedposition on information storage medium (optical disc) 9 using a focusedbeam spot.

1-1-1. Basic Function Achieving Means of InformationRecording/Reproduction Unit

As means for achieving the above basic functions, the informationrecording/reproduction unit executes the following processes. That is,

the unit traces a focused beam spot along tracks 112 on informationstorage medium 9;

the unit switches recording/reproduction/erase of information bychanging the amount of light of a focused beam spot with whichinformation storage medium 9 is irradiated; and

the unit converts externally input recording signal d into an optimalsignal to record it at high density and with a low error rate.

2. Structure of Mechanism Portion and Operation of Detection Portion

2-1. Basic Structure of Optical Head 202 and Signal Detection Circuit

2-1-1. Signal Detection by Optical Head 202

Optical head 202 basically comprises a semiconductor laser element (notshown) as a light source, a photodetector, and an objective lens. Alaser beam emitted by the semiconductor laser element is focused oninformation storage medium (optical disc) 9 via the objective lens (121in FIG. 2). The laser beam reflected by a light reflection film or lightreflective recording film (122 or 123 in FIG. 2) of information storagemedium (optical disc) 9 is photoelectrically converted by thephotodetector. A detection current obtained by the photodetectorundergoes current-voltage conversion by amplifier 213 to obtain adetection signal. This detection signal is processed by focus/trackerror detection circuit 217 or binarization circuit 212.

In general, the photodetector is divided into a plurality ofphotodetection regions, which individually detect changes in amount oflight with which the respective photodetection regions are irradiated.Respective detection signals undergo sum/difference calculations by thefocus/track error detection circuit 217, thus detecting focus and trackerrors. In this way, a change in amount of light reflected by the lightreflection film or light reflective recording film of informationstorage medium (optical disc) 9 is detected, thereby reproducing signalc on information storage medium 9.

2-1-2. Objective Lens Actuator Structure

The objective lens (121 in FIG. 2) that focuses a laser beam emitted bythe semiconductor laser element on information storage medium 9 ismovable in two axis directions in accordance with an output current fromobjective lens actuator driving circuit 218. The objective lens moves:

in a direction perpendicular to information storage medium 9 to correctfocus errors; and

in the radial direction of information storage medium 9 to correct trackerrors.

Such objective lens moving mechanism is called an objective lensactuator.

2-2A. Rotation Control System (Zone CAV Rotation Control) of InformationStorage Medium (Optical Disc)

Information storage medium (optical disc) 9 is mounted on turn table 221which is rotated by the driving force of spindle motor 204. Therotational speed (rotational velocity) of information storage medium 9is detected based on a reproduction signal obtained from informationstorage medium 9. That is, the detection signal (analog signal) outputfrom amplifier 213 is converted into a digital signal by binarizationcircuit 212, and PLL (Phase Lock Loop) circuit 211 generates a constantperiod signal (reference clock signal) based on that digital signal.Information storage medium rotational speed detection circuit 214detects the rotational speed of information storage medium 9 using thissignal, and outputs the detection value.

A correspondence table of the information storage medium rotationalspeed which corresponds to the radial position where data is reproducedor recorded/erased on information storage medium 9 is pre-stored insemiconductor memory 219. When a reproduction position or record/eraseposition is determined, controller 220 sets a target rotational speed ofinformation storage medium 9 by looking up information recorded insemiconductor memory 219, and sends that value to spindle motor drivingcircuit 215.

Spindle motor driving circuit 215 calculates the difference between thistarget rotational speed and the output signal (current rotational speed)of information storage medium rotational speed detection circuit 214,and supplies the driving current corresponding to that difference tospindle motor 204, thus controlling the rotational speed of spindlemotor 204 to be constant. The output signal from information storagemedium rotational speed detection circuit 214 is a pulse signal having afrequency corresponding to the rotational speed of information storagemedium 9, and spindle motor driving circuit 215 controls both thefrequency and pulse phase of this signal.

2-2B. Rotation Control System (CLV Rotation Control) of InformationStorage Medium (Optical Disc)

Information storage medium (optical disc) 9 is mounted on turn table 221which is rotated by the driving force of spindle motor 204. Therotational speed (rotational velocity) of information storage medium 9is detected based on a reproduction signal obtained from a wobbledgroove region (143 in FIG. 12 or the like) present on informationstorage medium 9. That is, the detection signal (analog signal) outputfrom focus/track error detection circuit 217 is converted into a digitalsignal by a binarization circuit (not shown) in information storagemedium rotational speed detection circuit 214, thus generating aconstant period signal (reference signal). Rotational speed detectioncircuit 214 detects the rotational speed of information storage medium 9using this reference signal, and outputs a difference signalcorresponding to the frequency/phase difference between that detectionvalue and a reference clock signal. Based on this difference signaloutput value, spindle motor driving circuit 215 supplies a predetermineddriving current to spindle motor 204 to make control to attain aconstant linear velocity (CLV).

2-3. Optical Head Moving Mechanism

To move optical head 202 in the radial direction of information storagemedium 9, optical head moving mechanism (feed motor) 203 is equipped.

3. Functions of Respective Control Circuits

3-1. Focused Beam Spot Trace Control

In order to perform focus or track error correction, a circuit forsupplying a driving current to an objective lens actuator (not shown) inoptical head 202 in accordance with the output signal (detection signal)from focus/track error detection circuit 217 is arranged. This circuitis objective lens actuator driving circuit 218. This circuit 218includes a phase compensation circuit for improving characteristics incorrespondence with the frequency characteristics of the objective lensactuator to attain quick response of objective lens movement up to thehigh frequency range.

In response to a command from controller 220, objective lens actuatordriving circuit 218 executes:

an ON/OFF process of focus/track error correction operation (focus/trackloop);

a process for moving the objective lens at low speed in a direction(focus direction) perpendicular to information storage medium 9(executed when focus/track loop is OFF); and

a process for moving a focused beam spot to a neighboring track byslightly moving in the radial direction (direction to cross tracks) ofinformation storage medium 9 using a kick pulse.

4. Various Operations Associated With Control System of MechanismPortion

4-1. Startup Control

When information storage medium (optical disc) 9 is mounted on turntable 221 and startup control is started, the processes are executed inaccordance with the following sequence.

1) Controller 220 sends a target rotational speed to spindle motordriving circuit 215, which supplies a driving current to spindle motor204, thus starting rotation of spindle motor 204.

2) At the same time, controller 220 issues a command (execution command)to feed motor driving circuit 216, which supplies a driving current tooptical head driving mechanism (feed motor) 203, thus moving opticalhead 202 to the innermost peripheral position of information storagemedium 9. At that time, it is confirmed if optical head 202 has reachedan inner peripheral portion beyond the information recording region oninformation storage medium 9.

3) When spindle motor 204 has reached the target rotational speed, thatstatus (status report) is output to controller 220.

4) Semiconductor laser driving circuit 205 supplies a current to thesemiconductor laser element in optical head 202 in correspondence with areproduction light amount signal sent from controller 220 torecording/reproduction/erase control waveform generation circuit 206,thus starting laser emission.

Note that an optimal irradiation light amount upon reproduction variesdepending on the types of information storage media (optical discs) 9.Upon startup, the lowest irradiation light amount value of those valuesis set.

5) The objective lens (121 in FIG. 2) in optical head 202 is moved to aposition farthest from information storage medium 9, and objective lensactuator driving circuit 218 is controlled to make the objective lensslowly approach information storage medium 9.

6) At the same time, focus/track error detection circuit 217 detects afocus error amount, and outputs status to controller 220 when theobjective lens has reached near an in-focus position.

7) Upon receiving that status, controller 220 issues a command toobjective lens actuator driving circuit 218 to enable the focus loop.

8) Controller 220 issues a command to feed motor driving circuit 216while the focus loop is ON to slowly move optical head 202 toward theouter periphery of information storage medium 9.

9) At the same time, a reproduction signal from optical head 202 ismonitored, and when optical head 202 has reached the recording region oninformation storage medium 9, controller 220 stops movement of opticalhead 202, and issues a command to objective lens actuator drivingcircuit 218 to enable the track loop.

10) An “optimal light amount upon reproduction” and “optimal lightamount upon recording/erase” recorded on the inner peripheral portion ofinformation storage medium (optical disc) 9 are reproduced, and arerecorded in semiconductor memory 219 via controller 220.

11) Furthermore, controller 220 sends a signal corresponding to that“optimal light amount upon reproduction” to recording/reproduction/erasecontrol waveform generation circuit 206, thus re-setting the emissionamount of the semiconductor laser element upon reproduction.

12) The emission amount of the semiconductor laser element uponrecording/erase is set in correspondence with the “optimal light amountupon recording/erase” recorded on information storage medium 9.

4-2. Access Control

4-2-1. Reproduction of Access Destination Information on InformationStorage Medium 9

Information that indicates locations and contents of informationrecorded on storage medium 9 varies depending on the types ofinformation storage medium 9, and is generally recorded in directorymanagement regions, navigation packs, or the like in information storagemedium 9. Note that the directory management regions are recordedtogether in the inner or outer peripheral region of information storagemedium 9. On the other hand, the navigation pack is contained in a VOBS(Video Object Set) complying with the data structure of a PS (ProgramStream) of MPEG2, and records information indicating the location of thenext video data.

When specific information is to be reproduced or recorded/erased,information in the above-mentioned region (information indicating thelocations and contents of information recorded) is reproduced, and anaccess destination is determined based on the reproduced information.

4-2-2. Coarse Access Control

Controller 220 calculates the radial position of the access destination,and detects the distance between that position and the current positionof optical head 202. As for the moving distance of optical head 202,velocity curve information that allows the head to reach the targetposition within a shortest period of time is stored in advance insemiconductor memory 219. Controller 220 reads that information, andcontrols movement of optical head 202 by the following method inaccordance with the velocity curve.

More specifically, controller 220 issues a command to objective lensactuator driving circuit 218 to disable the track loop, and thencontrols feed motor driving circuit 216 to start movement of opticalhead 202. When the focused beam spot has crossed a track on informationstorage medium 9, focus/track error detection circuit 217 generates atrack error detection signal. Using this track error detection signal,the relative velocity of the focused beam spot with respect toinformation storage medium 9 can be detected. Feed motor driving circuit216 calculates the difference between the relative velocity of thefocused beam spot obtained from focus/track error detection circuit 217,and target velocity information sent from controller 220, and feeds backthat result to the driving current to be supplied to optical headdriving mechanism (feed motor) 203, thus moving optical head 202.

In “optical head moving mechanism (feed motor) 203” mentioned above, africtional force always acts between a guide shaft and bushing orbearing (not shown). When the optical head moves at high speed, dynamicfriction acts. However, since the moving velocity of optical head 202 islow at the beginning of movement and immediately before stop, staticfriction acts. At that time, since the relative frictional forceincreases, the amplification factor (gain) of a current to be suppliedto optical head driving mechanism (feed motor) 203 is increased inresponse to a command from controller (especially, immediately beforestop).

4-2-3. Fine Access Control

When optical head 202 has reached the target position, controller 220issues a command to objective lens actuator driving circuit 218 toenable the track loop. The focused beam spot reproduces an address ortrack number of that portion while tracing along a track on informationstorage medium 9. The current focused beam spot position is detectedfrom that address or track number, and controller 220 calculates thenumber of error tracks from the reached target position and informsobjective lens actuator driving circuit 218 of the number of tracksrequired to move the focused beam spot. When objective lens actuatordriving circuit 218 generates a pair of kick pulses, the objective lensslightly moves in the radial direction of information storage medium 9,thus moving the focused beam spot to the neighboring track.

In objective lens actuator driving circuit 218, the track loop istemporarily disabled, and after kick pulses are generated a given numberof times corresponding to the information from controller 220, the trackloop is enabled again. Upon completion of fine access, controller 220reproduces information (address or track number) at the position wherethe focused beam spot traces, and confirms if it has accessed a targettrack.

4-3. Continuous Recording/Reproduction Erase Control

As shown in FIG. 6, a track error detection signal output fromfocus/track error detection circuit 217 is input to feed motor drivingcircuit 216. “Upon startup control” and “upon access control” mentionedabove, controller 220 controls feed motor driving circuit 216 not to usethe track error detection signal. After it is confirmed that the focusedbeam spot has reached the target track by access, some components of thetrack error detection signal are supplied as a driving current tooptical head driving mechanism (feed motor) 203. This control continuesduring the period in which a reproduction or recording/erase process isdone continuously.

Note that information storage medium 9 is mounted so that its centralposition has a slight eccentricity from that of turn table 221. Whensome component of the track error detection signal are supplied as adriving current, entire optical head 202 slightly moves incorrespondence with the eccentricity. When the reproduction orrecording/erase process is continuously done for a long period of time,the focused beam spot position gradually moves toward the outer or innerperiphery. When some components of the track error detection signal aresupplied as a driving current to optical head moving mechanism (feedmotor) 203, optical head 202 gradually moves toward the outer or innerperiphery in correspondence with that current. In this manner, the loadon track error correction of the objective lens actuator is reduced,thus attaining a stable track loop.

4-4. End Control

When a series of processes are complete and the operation is to beended, the process is done in accordance with the following sequence.That is,

1) controller 220 issues a command to objective lens actuator drivingcircuit 218 to disable the track loop;

2) controller 220 issues a command to objective lens actuator drivingcircuit 218 to disable the focus loop;

3) controller 220 issues a command to recording/reproduction/erasecontrol waveform generation circuit 206 to stop emission of thesemiconductor laser element; and

4) controller 220 informs spindle motor driving circuit 215 of zeroreference rotational speed.

5. Flow of Recording Signal/Reproduction Signal to Information StorageMedium

5-1. Signal Format Recorded on Information Storage Medium 9

In order to meet requirements:

of correcting recording information errors caused by defects oninformation storage medium 9;

of simplifying a reproduction processing circuit by setting zero DCcomponent of a reproduction signal; and

of recording information at highest possible density on informationstorage medium 9 for a signal to be recorded on information storagemedium 9, the information recording/reproduction unit (physical systemblock) performs “addition of an error correction function” and “signalconversion of recording information (signal modulation/demodulation)”,as shown in FIG. 6.

5-2. Flow of Signal Upon Recording

5-2-1. ECC (Error Correction Code) Appending Process

Information to be recorded on information storage medium 9 is input todata input/output interface 222 as recording signal d in the form of araw signal. This recording signal d is directly recorded insemiconductor memory 219, and then undergoes an ECC appending process,as described above, in ECC encoding circuit 208.

Upon completion of appending of inner-code PI and outer-code PO, ECCencoding circuit 208 reads data for one sector from semiconductor memory219, and transfers the read data to modulation circuit 207.

5-2-2. Signal Modulation

In order to make a DC component (DSV: Digital Sum Value) of areproduction signal approach 0 (zero), and to record information oninformation storage medium 9 at high density, signal modulation asconversion of a signal format is done in modulation circuit 207.Modulation circuit 207 and demodulation circuit 210 include a conversiontable indicating the relationship between a source signal and modulatedsignal. The signal transferred from ECC encoding circuit 208 issegmented into data each consisting of a plurality of bits in accordancewith a modulation scheme, and the segmented data are converted intoother signals (codes) by looking up the conversion table.

For example, when 8/16 modulation (RLL (2, 10) code) is used as themodulation scheme, two different types of conversion tables are present,and the conversion table to be looked up is switched as needed to makethe DC component (DSV) after modulation approach zero.

5-2-3. Recording Process on Information Storage Medium 9

Semiconductor laser driving circuit 205 operates to record informationfrom optical head 202 on information storage medium 9. At this time, asshown in FIG. 1 and (b) of FIG. 2, recording marks 127 are continuouslyformed along tracks 112 for respective continuous data recording units110, and gaps 111 are formed between neighboring continuous datarecording units 110.

Note that each continuous data recording unit (110, 131) is made up ofone whole ECC block (130 a) or a fraction of an integer (e.g., 133 or134 in FIG. 8) of one ECC block (130 b), as shown in FIG. 8. Note that“a fraction of an integer of one ECC block” indicates a case wherein oneECC block (130 b) contains a plurality of physical sectors (e.g., 7-0 to7-31 in FIG. 8), and a fraction of an integer of the plurality ofphysical sectors (7-0 to 7-15 or 7-16 to 7-31; 1/2 in this case) formone continuous data recording unit (133 or 134).

5-3. Flow of Signal Upon Reproduction

5-3-1. Binarization/PLL Circuit

As described in “signal detection by optical head 202”, a change inamount of light reflected by the light reflection film or lightreflective recording film of information storage medium (optical disc) 9is detected to reproduce a signal on information storage medium 9.Binarization circuit 212 converts that signal into a binary digitalsignal consisting of “1” and “0” using a comparator.

From the reproduction signal obtained by the binarization circuit, PLLcircuit 211 extracts a reference signal upon reproducing information.PLL circuit 211 incorporates a variable frequency oscillator. Thefrequency and phase of a pulse signal (reference clock) output from theoscillator are compared with those of the output signal from thebinarization circuit 212, and the comparison results are fed back to theoscillator output.

5-3-2. Signal Demodulation

Demodulation circuit 210 incorporates a conversion table (not shown)indicating the relationship between modulated and demodulated signals. Amodulated signal is restored to an original signal by looking up theconversion table in synchronism with the reference clock obtained by PLLcircuit 211. The restored (demodulated) signal is recorded insemiconductor memory 219.

5-3-3. Error Correction Process

Error correction circuit 209 detects any errors of a signal saved insemiconductor memory 219 using inner-code PI and outer-code PO, and setspointer flags of error positions. After that, error correction circuit209 corrects a signal at the error positions in accordance with theerror pointer flags while reading out the signal from semiconductormemory 219, removes inner-code PI and outer-code PO, and transfers thesignal to data input/output interface 222. A signal sent from ECCencoding circuit 208 is output as reproduction signal c from datainput/output interface 222.

Parameters used in the control sequences of respective processes and therespective processes in the apparatus shown in FIG. 6 are written incontrol program/parameter ROM 220 b in controller 220 as firmware. Amicroprocessing unit MPU (not shown) of controller 220 executes acontrol program in ROM 220 b using worm RAM 220 a as a work area, thusexecuting the aforementioned processes.

The format process sequence executed in the apparatus shown in FIG. 6will be explained below using the flow chart shown in FIG. 7. Thisprocess is executed in ECC encoding circuit 208 shown in FIG. 6, anddetailed control is made by controller 220. FIG. 7 shows the sequence ofthe data conversion process (format conversion process) shown in FIGS. 3to 5.

Initially, physical sector information is set (step ST1). With thissetting, a plurality of pieces of physical sector information 4-0 to4-31 ((c) of FIG. 3) are set (segmented into main data in units of 2048bytes). In this case, the plurality of pieces of physical sectorinformation 4-0 to 4-31 are set in correspondence with the size of aplurality of pieces of logical sector information 3-0 to 3-31 ((b) ofFIG. 3). That is, user data to be recorded is handled in units of 2048bytes.

Subsequently, a 2068-byte data sector is generated from 2048-byte maindata, 16-byte auxiliary data, and a 4-byte error detection code (EDC)(step ST2). Note that the 16-byte auxiliary data contains 4-byte data IDdata (PID), a 2-byte error detection code (IED) for the data ID, and10-byte reserve data (RSV).

Note that the PID records a sector number used to identify a datasector, and sector information used to identify the contents of the datasector. The IED is used to detect any errors generated in the PIDportion. The RSV is used to record other kinds of auxiliary information(e.g., copyright management information). The EDC is used to detect anyerrors generated in 2064-byte main data and auxiliary data. The datasectors are arranged in a 188 (columns)×11 (rows) matrix.

Scramble data is added to 2048-byte main data of each data sector (stepST3).

Data sector rows are re-arranged depending on whether the sector numberis even or odd (step ST4).

A sector block is generated by vertically stacking 32 continuous datasectors, which are re-arranged depending on their sector numbers (stepST5). The data sectors which are vertically stacked are arranged in a376 (columns)×176 (rows) matrix.

The sector block is horizontally segmented into two blocks to encodeerror correction codes (step ST6). Note that the 188 (columns)×176(rows) blocks after segmentation undergo encoding in the columndirection to generate outer-code parity data (PO) for 16 rows. Thisouter code uses a REED Solomon code of RS(192, 176, 17). Subsequently,inner-code encoding is done in the row direction to generate inner-codeparity data (PI) for 12 columns. This inner code uses a REED Solomoncode of RS(200, 188, 13).

The ECC block undergoes row interleave to distribute 16 right and leftrows of PO data into the block (step ST7; see FIG. 5). In this case, 32rows (=16×2) of PO data are distributed row by row to sectors. At thistime, PO rows of the left block of the two horizontally segmented blocksare inserted after the lowermost row of an odd sector consisting of onlyfive rows, and PO rows of the right block of the two horizontallysegmented blocks are inserted after the lowermost row of an even sectorconsisting of only five rows.

With the aforementioned process, physical sector data is completed (stepST8).

Subsequently, zigzag recording across two rows is done (step ST9).

A modulation process is executed (step ST10). In this case, if a bitsequence of data to be recorded is directly recorded on medium 9, thecharacteristic feature of the recording data sequence does not match therecording characteristics of medium 9, and efficient recording cannot bedone. In consideration of the recording characteristics of medium 9, adata pattern is converted according to a predetermined conversion rule.For example, the modulation scheme includes an 8/16 modulation schemefor converting 1-byte data into a 16-bit pattern, an 8/12 modulationscheme for converting 1-byte data into a 1.5-byte pattern, a 12/18modulation scheme for converting 12-bit data into an 18-bit pattern, andthe like. Any one of these schemes comprises a plurality of conversiontables and a logic circuit for selecting the conversion table.Especially, since the 12/18 modulation scheme that converts 1.5-bytedata has a characteristic of expanding an error at one position to 1.5bytes, it is effective for the process executed in step ST9 todistribute errors upon reproduction.

Via steps ST1 to ST10, zigzag recording according to the setup in stepST9 is done for medium 9. In this recording, data recording iscontinuously done for respective continuous data recording units 110, asshown in FIG. 1. In this case, recording is controlled to form gaps 111with length δ between neighboring continuous data recording units 110.

FIG. 8 is a view for explaining the data recording method on theinformation storage medium (recordable optical disc using a blue laser)according to another embodiment of the present invention.

The physical data length of recording information 114 in FIG. 1 nearlymatches the data length (the length of ECC block 130 a in FIG. 8) aftermodulation of data of the ECC block shown in FIGS. 3 and 4, as describedabove.

When a radial position where the length per round of information storagemedium 9 matches an integer multiple of length L+δ has been reached, ECCblock 130 b is segmented into two blocks, and continuous data recordingunit 131 b which is obtained by appending VFO field 113b to former halfdata 133 of ECC block 130 b to have physical length J is recorded in thedirection of tracks 112.

Gap 111 c with length δ is formed after such continuous data recordingunit 131 b, and continuous data recording unit 131 c obtained byappending VFO field 113c to latter half data 133 of ECC block 130 b tohave physical length J is recorded after gap 111 c in the direction oftracks 112. As can be seen from FIG. 8, since length “δ+J+δ+J” isdifferent from length L+δ, gaps 111 do not come to neighboring positionsbetween neighboring tracks (112 a and 112 b) at that radial position(the radial positions of tracks 112 a and 112 b in FIG. 8).

In FIG. 8, the half of data obtained by modulating ECC block 130 b isrecorded and arranged in continuous data recording unit 131. However,the scope of the present invention is not limited to this. For example,a plurality of arbitrary physical sector data (7-0 to 7-15 and 7-16 to7-31 in the example in FIG. 8) may be recorded and arranged, or aplurality of ECC blocks 130 may be recorded and arranged together insingle continuous data recording unit 131.

FIG. 9 is a view for explaining necessity of gaps (groove gaps) δ in theinformation storage medium according to the present invention.

A problem posed when δ assumes too small a value will be explained belowusing FIG. 9. When spindle motor 204 shown in FIG. 6 is free from anyrotation nonuniformity (ideal state), pairs of continuous data recordingunits 110 and gaps 111 are recorded along tracks 112 without anyvariations of length (L+δ), as shown in (a) of FIG. 9. However, when therotational speed of spindle motor 204 locally increases (due to rotationnonuniformity), the end position of continuous data recording unit 110 ashifts backward, and gap 111 b is narrowed down. Furthermore, in theworst case, the end position of continuous data recording unit 110 a mayenter the head position of continuous data recording unit 110 b that hasalready been recorded at the subsequent location, and data overlapportion 116 may be generated.

When recording layers 122 and 123 of information storage medium 9 aremade up of a phase-change type recording film, data overlap portion 116is overwritten by rear data of leading continuous data recording unit110 a, and first data of continuous data recording unit 110 b isdestroyed.

Rotation control of spindle motor 204 is made using a wobble signalobtained from wobbled groove 143 shown in FIG. 12. Therefore, let f bethe rotation nonuniformity amount of spindle motor 204, and τ be thewobble period of wobbled groove 143. Then, the shift amount of last dataof continuous data recording unit 110 a due to rotation nonuniformity ofspindle motor 204 is given by “τf”.

Therefore, in order to avoid the problem resulting from the data overlapportion shown in (b) of FIG. 9, length δ of gap 111 must be set tosatisfy:δ≧τf   (7)

The rotation nonuniformity amount of spindle motor 204 (the practicalrotation nonuniformity amount, including the influence of eccentricity,of optical disc 9, which is actually set on table 221 rotated by motor204) normally depends on the eccentricity of information storage medium9. If the eccentricity of information storage medium 9 is ±100 μm,rotation nonuniformity amount f due to this eccentricity is around 0.1%.In this case, inequality (7) is rewritten as:δ24 0.001τ  (8)

Inequality (7) or (8) can define the lower limit of gap δ, andinequality (4), (5), or (6) mentioned above can define the upper limitof gap δ.

Note that the value of gap δ, the lower limit of which is defined byinequality (7) or (8) cannot often satisfy inequality (6) (δ≦D/4 orδ≦ttan{sin⁻¹(NA/n)}/2) mentioned above due to (practical) rotationnonuniformity of spindle motor 204 or other factors. A measure againstsuch case will be explained below.

As described above in (b) of FIG. 2, when long gap regions 111 withlength δ align in the radial direction of information storage medium 9,inter-layer crosstalk takes place. This inter-layer crosstalk becomesconspicuous with increasing length δ of gap 111 (if δ=0, no inter-layercrosstalk due to gaps 111 occurs). Hence, if length δ of gaps 111 cannotbe shortened due to rotation nonuniformity or the like, the positions ofgaps 111 shift, i.e., gaps 111 are arranged at non-neighboring positionsbetween neighboring tracks, thus reducing inter-layer crosstalk. One ofexamples of such position shift methods of gaps 111 has already beenexplained with reference to FIG. 8. In addition, as an example of theposition shift method of gaps 111, a method shown in FIG. 10 isavailable.

FIG. 10 shows an application (modification) of FIG. 8. In FIG. 8, thephysical periodic length of gaps 111 is changed to lay out gaps 111 atnon-neighboring positions between neighboring tracks (112 a and 112 b).Alternatively, in FIG. 10, the physical periodic length of gaps 111 isnot macroscopically changed, but the position of gap 111 is shifted atonly a position where gaps may be located at neighboring positionsbetween neighboring tracks (112 a and 112 b).

In FIG. 10, at many locations in information storage medium 9, each ECCblock 130 b is segmented into two blocks, 16 sectors from physicalsectors 7-0 to 7-15 are assigned to continuous data recording unit 131 bas former half data 133 of ECC block 130 b, and another 16 sectors fromphysical sectors 7-16 to 7-31 are assigned to continuous data recordingunit 131 c as latter half data 134 of ECC block 130 b.

At the radial position (that satisfies inequality (7)) of informationstorage medium 9 at which gaps 111 are located at neighboring positions(position of point A) between neighboring tracks with this layoutmethod, the position of gap 111 e is shifted to the position of point B.

That is, at this location (position of point B), 15 sectors fromphysical sectors 8-1 to 8-14 are assigned to continuous data recordingunit 137 as former half data 133 of ECC block 130 c. As a result, thephysical length of continuous data recording unit 137 is shortened from“J” to “J−α”. At the same time, 17 sectors from physical sectors 8-15 to8-31 are assigned to continuous data recording unit 138 as latter halfdata 134 of ECC block 130 c. As a result, the physical length ofcontinuous data recording unit 132 is prolonged from “J” to “J+α”. As aresult, the position of gap 111 e is shifted.

In this way, the numbers of sectors to be stored in continuous datarecording units 137 and 138 are changed before and after gap 111 e(i.e., the total length of continuous data recording units 137+138remains the same, but the lengths of continuous data recording units 137and 138 are changed by ±α, thus shifting the position of gap 111 e froma neighboring position of point A to point B.

In the embodiment shown in FIG. 8, data obtained by segmenting ECC block130 into 1/M data is assigned to one of continuous data recording units131 to 133. In the embodiment shown in FIG. 10, ECC block 130 issegmented into two data (M=2), which are assigned to the continuous datarecording units. However, this embodiment is not limited to this, andother values such as 4, 8, 16, and the like may be used as the value M.

The aforementioned conditions of inequalities (4) to (6) are met onlywhen gaps 111 align in the radial direction, as shown in (b) of FIG. 2.Let L be the physical length of continuous data recording unit 110 inthe direction along tracks 112 of information storage medium 9. Then,the condition of inequality (6) is satisfied only when the center oflaser beam 120 traces a position of radius r₀ which satisfies:N(L+δ)=2πr ₀   (9)with respect to integer value N.

However, at the position of radius r (r≠r₀), since we generally have:N(L+δ)=2πr−ζ  (10)the positions of gaps 111 do not align but shift from each other, asshown in FIG. 11.

FIG. 11 is a view for explaining the maximum allowable range of gaps(groove gaps) on the information storage medium according to the presentinvention.

The embodiment of the present invention adopts CLV (Constant LinearVelocity) as the recording method. In FIG. 11, the central position ofgap 111 or 115 at the position of radius r of information storage medium9 will be considered as a reference.

Let Pt be the track pitch. Then, the shift amount between the centralpositions of gaps 111 or 115 on neighboring tracks in the directionalong the tracks (in the circumferential direction of informationstorage medium 9) is given by:2πPt+ζ  (11)

In FIG. 11, the shift amount of the central position of gap 111 or 115at the m-th track position counted from a track with radius r from thegap central position at the immediately preceding track position isgiven by:2πPt·m+ζ  (12)For this reason, total shift amount X from the reference position(central position of gap 111 or 115 at the position of radius r) isgiven by:X=Σ{2πPt·m+ζ}  (13)

As in the case of (b) of FIG. 2, the spot diameter of laser beam 120that causes the influence of inter-layer crosstalk is also D in FIG. 11.Since the number of tracks included within length D is D/Pt, the totalof equation (13) is obtained by calculating the sum from m=0 to m=D/Ptand is given by: $\begin{matrix}\begin{matrix}{X = {{\pi\quad{{Pt}\left( {D/{Pt}} \right)}\left( {{D/{Pt}} + 1} \right)} + {\zeta\quad{D/{Pt}}}}} \\{= {\left\{ {{\pi\left( {D + {Pt}} \right)} + \zeta} \right\}{D/{Pt}}}}\end{matrix} & (14)\end{matrix}$

If gaps 111 a to 111 f with sufficiently small length δ2 are present inFIG. 11, the influence of inter-layer crosstalk may be relatively small.By contrast, if gaps 115 a to 115 f with sufficiently large length δ1are present, no recording mark is present within most of the area inlaser beam 120 in the state shown in FIG. 11, and large inter-layercrosstalk appears.

As shown in FIG. 11, when start position G of gap 115 a located at theendmost position in laser beam 120, and end position H of gap 115 flocated at the opposite end position in laser beam 120 align in theradial direction (positions G and H nearly match in the circumferentialdirection), the influence of inter-layer crosstalk appears clearly. Inthis case, the distance from the central position of gap 115 a to startposition G is equal to that from the center of gap 115 f to end positionH, i.e., δ1/2. As a result, X=δ1 at that time and, from equation (14),we have:δ1={π(D+Pt)+ζ}D/Pt   (15)

Therefore, since a condition that can reduce the influence ofinter-layer crosstalk in the state shown in FIG. 11 is δ<δ1, we have:δ≦{π(D+Pt)+ζ}D/Pt   (16)

Since the average at every positions on information storage medium 9 is:ζ=(L+δ)/2≈L/2   (17)substitution of equation (17) into inequality (16) yields:δ≦{π(D+Pt)+L/2}D/Pt   (18)

In a minimum state, since ζ=0, inequality (16) is rewritten as:δ≦π(D+Pt)D/Pt   (19)That is, inequality (19) must be satisfied as the inter-layer crosstalkreduction that pertains to length δ of gaps.

FIG. 12 is a view for explaining an information storage medium formedwith a mark that determines a recording start position according tostill another embodiment of the present invention.

Recording start position determination mark 141 recorded on informationstorage medium 9 is reproduced by optical head 202 in FIG. 6, and issent to focus/track error detection circuit 217 via amplifier 213. Infocus/track error detection circuit 217, the presence/absence of mark141 is detected as a given component of a track error detection signal.Note that the frequency of a detection signal obtained from recordingstart position determination mark 141 is much higher than that of thetrack error detection signal. For this reason, by frequency-separatingthese two signals, mark 141 can be easily detected. Since the twosignals have a large frequency difference, the adverse influence of thepresence of mark 141 on the track error detection signal can be reduced.

A wobbled pattern (repeated pattern of 2τ and τ) of the recording startposition determination mark 141 portion is different from that (repeatedpattern of τ alone) of a portion other than the mark. That is, the mark141 portion has a unique wobbled pattern (a kind of address). For thisreason, the detected “repeated pattern of 2τ and τ” can be reliablydetermined (specified) as mark 141.

Since the embodiment of the present invention records data using CLV,gaps 111 have different positions in the direction of rotation angledepending on radial positions of information storage medium 9, and theposition of recording start position determination mark 141 in thedirection of rotation angle shifts accordingly, as shown in FIG. 11. Byexploiting this feature, the radial position of a location where thehead currently traces can be detected by detecting only the position ofrecording start position determination mark 141 in the direction ofrotation angle.

According to inequality (19) above, gap 111 or 115 must be set to havesmall physical length δ (δ1 or δ2 in FIG. 11). In this case, since gap111 or 115 has sufficiently small physical length δ, when data of onlyone continuous data recording unit 110 is rewritten, the rewrite startposition is required to have high precision. If the rewrite startposition precision is low, the previous and next continuous datarecording unit positions may be overwritten upon rewriting only onecontinuous data recording unit 110.

In order to assure this high precision, in the embodiment shown in FIG.12, recording start position determination mark 141 is recorded inadvance on medium (recordable optical disc) 9 in the form of wobblemodulation. This is a great characteristic feature of the embodiment ofthe present invention.

This recording start position determination mark 141 has the followingfeatures:

(a) Wobble modulation for wobbling a pre-groove which has a continuousgroove shape and forms track 112 to the right and left is made. Thewidth of the pre-groove which is wobbled to the right and left ismaintained constant everywhere.

<Comment on a> Since the groove width is constant everywhere, even whena focused reproduction laser beam is traced on recording start positiondetermination mark 141, the reflectance of light from that mark can bemaintained constant. Therefore, recording marks 127 can be directlyformed on recording start position determination mark 141. Even whensignal reproduction using a change in amount of light reflected byrecording marks 127, which are directly formed on recording startposition determination mark 141, is made, a reproduction signal is freefrom the influence of recording start position determination mark 141.

(b) Recording marks 127 corresponding to immediately precedingcontinuous data recording unit 110 a can be recorded in at least aportion in recording start position determination mark 141.Alternatively, recording marks 127 can be recorded over whole recordingstart position determination mark 141.

<Comment on b> In order to improve the recording efficiency oninformation storage medium 9, the physical length of gap 111 b ispreferably reduced as much as possible. As shown in FIG. 12, whenrecording marks 127 corresponding to immediately preceding continuousdata recording unit 110 a can be recorded in at least a portion ofrecording start position determination mark 141, information recordingis allowed on recording start position determination mark 141, thusimproving the recording efficiency and increasing the recording capacityof the entire information storage medium.

(c) The macroscopic duty ratio of wobble modulation of wobbled grooveregion 143 is matched with that of recording start positiondetermination mark 141.

<Comment on c> In wobbled groove region 143, the ratio of right and leftportions of wobbles is always set at 50% using a sine waveform.Likewise, the right-and-left wobbling ratio of recording start positiondetermination mark 141 by wobble modulation is maintained at 50%. As aresult, generation of an offset to a track error detection signal at theposition of recording start position determination mark 141 can beprevented.

For example, when the right wobbling period of recording start positiondetermination mark 141 is macroscopically longer than the left wobblingperiod, even when just the center of track 112 (pre-groove) is traced, atrack offset, which is detected as a track error signal by the push-pullmethod as if a slightly left portion of track 112 were traced, isgenerated.

(d) Recording start position determination mark 141 is formed by wobblemodulation while assuring the reference frequency (1/τ: slot intervalτ/2) of wobble groove region 143.

<Comment on d> In wobbled groove region 143 in FIG. 12, a groove iswobbled at period τ. The distance from a position where the centralposition of a wobble is passed until the central position is crossedagain is called a slot interval (having the same meaning as the channelbit interval in general data). Wobbled groove region 143 in FIG. 12 hasa slot interval of τ/2. The reference frequency upon recording, thereference frequency used in PLL (Phase Lock Loop) upon reproduction, orrotation synchronization control of spindle motor 204 executes PLL withreference to slot interval τ/2 detected from this wobbled groove. If thereference frequency has changed within recording start positiondetermination mark 141, PLL steps out in recording start positiondetermination mark 141, and the recording/reproduction process androtation control of the spindle motor become unstable. For this reason,the reference frequency in recording start position determination mark141 is maintained constant to be 1/τ.

A pattern in recording start position determination mark 141 shown inFIG. 12 alternately repeats a wobble of period “2τ” and that of period“t” as in wobbled groove region 143 for four cycles. In the wobbledportion having period “2τ”, the interval from when a wobble exceeds thecenter once until it passes the center again is just “τ”. Since thisvalue corresponds to a value exactly twice slot interval τ/2, slotinterval τ/2 (i.e., reference frequency 1/τ) is maintained unchanged inthis region. As a result, PLL is kept enabled irrespective of inside oroutside recording start position determination mark 141, and therecording/reproduction process and rotation control of the spindle motorcan be stably done.

(e) Recording preparation region 142 is assured between recording startposition determination mark 141 and the recording start position ofcontinuous data recording unit 110 b, so that the informationrecording/reproduction apparatus becomes ready to record while a focusedbeam spot passes by this recording preparation region 142.

<Comment on e> The S/N ratio of a wobble modulation signal obtained fromthe wobbled groove is very poor, and the probability that the startposition of recording start position determination mark 141 is alwaysdetected is low. Hence, in the embodiment of the present invention,since a wobble with period “2τ” and that with period “τ” are alternatelyrepeated for four cycles, the information recording/reproductionapparatus can find recording start position determination mark 141somewhere in four cycles.

Once the information recording/reproduction apparatus can find aposition within recording start position determination mark 141, thegate (detection window) of a high-performance position detection circuitis opened to detect the end position of recording start positiondetermination mark 141 with high precision. Since the physical length ofrecording preparation region 142 is set to be a specific value inadvance, if the end position of recording start position determinationmark 141 is detected, the recording process is started after an elapseof a time interval required to pass recording preparation region 142,which is set at the specific value, thus forming recording marks 127from the head position of continuous data recording unit 110 b. In thismanner, since recording preparation region 142 is laid out immediatelyafter recording start position determination mark 141, the end positiondetection precision of recording start position determination mark 141can be improved. As a result, the low head position detection precisioncan be allowed, and a price reduction of a wobble modulation detectioncircuit can be achieved. Since the end position detection precision ofrecording start position determination mark 141 is improved, the startposition precision of continuous data recording unit 110 b can begreatly improved compared to the prior art.

Note that the groove pattern of recording preparation region 142 in FIG.12 has the same amplitude and period of that of wobbled groove region143.

As the pattern of recording start position determination mark 141, asingle wobble with period “2τ” and a single wobble with period “τ” arealternately repeated for four cycles, as shown in FIG. 12. However, thenumber of times of repetition in recording start position determinationmark 141 is not limited to four, but an arbitrary number of times ofrepetition can be selected. The pattern of recording start positiondetermination mark 141 is not limited to that shown in FIG. 12, but anarbitrary pattern can be set as long as conditions (a) to (c) aresatisfied within the scope (feature) of the present invention.

A method of overwriting and/or additionally writing data on informationstorage medium 9 using recording start position determination mark 141pre-recorded on information storage medium 9, as shown in FIG. 12, willbe explained below with reference to FIG. 13.

Controller 220 in FIG. 6 receives an instruction indicating a positionwhere information recording is to be done (i.e., recording location ofrecording information) on information storage medium 9 shown in FIG. 12or 1 (step ST111).

Before information is recorded or rewritten on information storagemedium 9, the position of recording start position determination mark141 in the direction of rotation angle at the radial position whererecording or rewrite is made is predicted on the basis of the recordinglocation instructed in step ST111 (step ST112).

After the position of mark 141 is predicted, data (corresponding torecording information 114 in FIG. 1 or 133, 134 in FIG. 8/10) ofcontinuous data recording unit 110 (131 in FIG. 8 or 137, 138 in FIG.10) is generated (step ST113). VFO field 113 is appended to the head ofdata of continuous data recording unit 110 generated in this way (stepST114).

Subsequently, the recording start position (the position predicted instep ST112) is accessed (step ST115). In this access, it is determinedif the unique pattern (repeated pattern of 2τ and τ) of recording startposition determination mark 141 is detected at the predetermined angularposition (the position predicted in step ST112) (step ST116), thuschecking if the predetermined radial position has been reached, or if atrack error has occurred during tracing. If mark 141 cannot be detectedat the predetermined position (NO in step ST116), it is determined thataccess cannot reach the predetermined position or a track error hasoccurred during tracking, and the access process is executed again (stepST115).

As described above, in the example shown in FIG. 12, since an identicalpattern (repeated pattern of 2τ and τ) is repeated four cycles asrecording start position determination mark 141, the informationrecording/reproduction apparatus in FIG. 6 can find mark 141 somewherein four cycles. If the information recording/reproduction apparatusfinds a position within recording start position determination mark 141(YES in step ST116), the gate (detection window) of a high-performanceposition detection circuit in the information recording/reproductionapparatus is opened to begin to prepare for detection of the endposition of recording start position determination mark 141 with highprecision (step ST117). That is, if the unique pattern of recordingstart position determination mark 141 is detected (YES in step ST116),recording preparation is made during a period which has a pattern endpoint of mark 141 as a start point and has a duration corresponding tothe length of recording preparation region 142 (step ST117).

As shown in FIG. 12, since no wobble signal with period “2τ” appearwithin recording preparation region 142, the boundary region betweenrecording start position determination mark 141 and recordingpreparation region 142 can be detected by utilizing this change inpattern.

Upon detection of the end position of recording start positiondetermination mark 141 (boundary position between mark 141 and recordingpreparation region 142), the control waits for an elapse of apredetermined time interval (a period corresponding to the length ofrecording preparation region 142) required to pass recording preparationregion 142, and a continuous recording process corresponding to thelength of continuous data recording unit 110 is executed (step ST118).

During recording (NO in step ST119), steps ST115 to ST118 are repeated.If data to be recorded does not remain (YES in step ST119), the processin FIG. 13 ends.

FIG. 14 is a flow chart for explaining a forming process of gap δ in therecording method according to the embodiment of the present invention.In this recording method, optical disc 9 which has wobbled grooves alongspiral tracks 112, and continuously undergoes data recording forrespective recording units (ECC blocks) along tracks 112 while beingrotated is used.

Data for one ECC block ((f), (g) of FIG. 4) is generated (step ST20),and recording marks 127 corresponding to the generated data are formedon track 112 of disc 9 (step ST21).

Gap δ (e.g., 111d in FIG. 10) is formed after the end of the recordedECC block (e.g., 130 b in FIG. 10), and the head of the next ECC block(e.g., 130 c in FIG. 10) is laid out (step ST22). Recording marks 127for the next ECC block (130 c) are formed on track 112 (step ST23). Theaforementioned operations (steps ST20 to ST23) are repeated duringrecording (NO in step ST24).

In the process shown in FIG. 14, when data recording is done (step ST23)while forming predetermined gap δ between neighboring ECC blocks alongtrack 112 (step ST22), the recording system (202 to 208) and rotationdriving system (204, 214, 215) in FIG. 6 are controlled so that gap δsatisfies “δ≧τf” where τ is the wobble period of the wobbled groove andf is the allowable rotation nonuniformity of rotation driving.

Furthermore, the recording system (202 to 208) and rotation drivingsystem (204, 214, 215) in FIG. 6 are controlled to satisfy at least oneof inequalities (4) to (6), inequality (7) or (8), and inequality (19).

Note that the present invention is not limited to the aforementionedembodiments, and various modifications may be made without departingfrom the scope of the invention when it is practiced. The respectiveembodiments may be combined as needed as long as possible, and combinedeffects can be obtained in such case.

Furthermore, the embodiments include inventions of various stages, andvarious inventions can be extracted by appropriately combining aplurality of required constituent elements disclosed in thisapplication. For example, even when some required constituent elementsare deleted from all the required constituent elements disclosed in theembodiments, the deleted elements are compensated for as needed by knowntechniques when the extracted invention is practiced.

<Gist of Respective Embodiments>

[Basic Point]

Data are continuously recorded for respective ECC blocks (recordingunits) along tracks 112 on information storage medium 9, and gaps δ areformed between neighboring ECC blocks (recording units) along tracks 112(FIGS. 1, 12, and the like).

[Peripheral Point]

(a) An allowable minimum value that δ can assume is specified(inequality (8) and the like);

(b) An allowable maximum value that δ can assume is specified(inequality (δ) and the like); and

(c) When the allowable maximum value that δ can assume is exceeded, thegap positions of neighboring recording units are shifted betweenneighboring tracks (FIGS. 8, 10, and the like).

As described above, according to the embodiments of the presentinvention, the following effects can be obtained in correspondence withthe following arrangements.

<1A> An information storage medium which has a wobbled groove alongspiral tracks (112) and continuously undergoes data recording forrespective predetermined recording units (ECC blocks) along the tracks(112) while being rotated, characterized in that the continuous datarecording can be done to form a predetermined gap δ between theneighboring predetermined recording units (ECC blocks) along the tracks(112), and the predetermined gap δ satisfies “δ≧τf” where τ is thewobble period of the wobbled groove and f is the allowable rotationnonuniformity of rotation.

<1B> An information recording method that uses an information storagemedium which has a wobbled groove along spiral tracks (112) andcontinuously undergoes data recording for respective predeterminedrecording units (ECC blocks) along the tracks (112) while being rotated,characterized in that upon executing the continuous data recording toform a predetermined gap δ between the neighboring predeterminedrecording units (ECC blocks) along the tracks (112), the predeterminedgap δ satisfies “δ≧τf” where τ is the wobble period of the wobbledgroove and f is the allowable rotation nonuniformity of rotation.

<1C> An information recording/reproduction apparatus that uses aninformation storage medium which has a wobbled groove along spiraltracks (112) and continuously undergoes data recording for respectivepredetermined recording units (ECC blocks) along the tracks (112) whilebeing rotated, and comprises a spindle motor (204) for rotating theinformation storage medium (9), recording system means (202-208) forforming recording marks (127) for respective predetermined recordingunits (ECC blocks) on the tracks (112) of the information storage medium(9) rotated by the spindle motor (204), and reproduction system means(202, 203, 213-209) for reading information of the recording marks (127)from the information storage medium (9), characterized in that a gap δwhich satisfies “δ≧τf” where τ is the wobble period of the wobbledgroove and f is the allowable rotation nonuniformity of the spindlemotor (204) is formed between the neighboring predetermined recordingunits (ECC blocks) along the tracks (112).

According to the arrangements of <1A> to <1C>, since recording is doneto form a gap (δ) between neighboring predetermined recording units (ECCblocks), two successive recording units can be prevented fromoverlapping even when a rotation driving mechanism (spindle motor)suffers rotation nonuniformity, and recorded data can be prevented frombeing destroyed (due to destruction of some recording marks when anoverlapping portion is formed), thus assuring high data reliability.Since no prepit headers are required unlike the prior art, the capacitycan be increased accordingly.

<2A> An information storage medium characterized in that uponcontinuously executing data recording for respective predeterminedrecording units (ECC blocks) along the tracks (112) on the informationstorage medium (9), recording can be done to form a gap (δ) between thepredetermined recording units (ECC blocks) along the tracks (112).

<2B> An information recording method characterized in that uponcontinuously executing data recording for respective predeterminedrecording units (ECC blocks) along the tracks (112) on the informationstorage medium (9), recording is done (ST22) to form a gap (δ) betweenthe predetermined recording units (ECC blocks) along the tracks (112).

<2C> An information recording/reproduction apparatus characterized inthat upon continuously executing data recording for respectivepredetermined recording units (ECC blocks) along the tracks (112) on theinformation storage medium (9), recording is done to form a gap (δ)between the predetermined recording units (ECC blocks) along the tracks(112).

According to the arrangements of <2A> to <2C>, since recording is doneto form a gap (δ) between neighboring predetermined recording units (ECCblocks), two successive recording units can be prevented fromoverlapping even when a rotation driving mechanism (spindle motor)suffers rotation nonuniformity, and recorded data can be prevented frombeing destroyed (due to destruction of some recording marks when anoverlapping portion is formed), thus assuring high data reliability.Since no prepit headers are required unlike the prior art, the capacitycan be increased accordingly.

<3A> An information storage medium characterized in that the informationstorage medium (9) is a one-sided, recording multilayer (122, 123) typedisc-shaped medium (9) having spiral tracks (112) with a track pitch Pt,data recording is optically done on the tracks (112) with the trackpitch Pt via an objective lens (121) having a numerical aperture NA andan intermediate layer (124) having a refractive index n and thickness t,and a length δ of the gap present between the predetermined recordingunits (ECC blocks) satisfies “δ≦π(D+Pt) D/Pt” (for D=2ttan{sin⁻¹(NA/n)}).

<3B> An information recording method characterized in that aninformation storage medium (9) is a one-sided, recording multilayer(122, 123) type disc-shaped medium (9) having spiral tracks (112) with atrack pitch Pt, data recording is optically done on the tracks (112)with the track pitch Pt via an objective lens (121) having a numericalaperture NA and an intermediate layer (124) having a refractive index nand thickness t, and a length δ of the gap present between thepredetermined recording units (ECC blocks) satisfies “δ≦π(D+Pt) D/Pt”(for D=2t tan{sin⁻¹(NA/n)}).

<3C> An information recording/reproduction apparatus characterized inthat an information storage medium (9) is a one-sided, recordingmultilayer (122, 123) type disc-shaped medium (9) having spiral tracks(112) with a track pitch Pt, data recording is optically done on thetracks (112) with the track pitch Pt via an objective lens (121) havinga numerical aperture NA and an intermediate layer (124) having arefractive index n and thickness t, and a length δ of the gap presentbetween the predetermined recording units (ECC blocks) satisfies“δ≦π(D+Pt) D/Pt” (for D=2t tan{sin⁻¹(NA/n)}).

According to the arrangements of <3A> to <3C>, in a one-sided,two-recording layer type information storage medium on which informationcan be read from a plurality of recording layers from one surface side,even when the already recorded portion and non-recorded portion have alight reflectance difference, inter-layer crosstalk due to the influenceof the presence/absence of recording marks on the other recording layercan be greatly reduced, and high reliability of a reproduction signalcan be assured.

<4A> An information storage medium characterized in that uponcontinuously executing data recording for respective recording units(ECC blocks) along spiral tracks (112) on a disc-shaped informationstorage medium (9) having a center of rotation (center of 10), recordingis done to form a gap (δ) between the predetermined recording units (ECCblocks) along the tracks (112), and an angular position (A) of the gap(δ) formed on one of at least one pair of neighboring tracks (112 a, 112b) of the tracks (112) with respect to the center of rotation (center of10) is different from an angular position (B) of the gap (δ) formed inthe other (112 b) of the neighboring tracks with respect to the centerof rotation (center of 10).

<4B>An information recording method that continuously executes datarecording for respective recording units (ECC blocks) along spiraltracks (112) on a disc-shaped information storage medium (9) having acenter of rotation (center of 10) to form a gap (δ) between thepredetermined recording units (ECC blocks) along the tracks (112),characterized in that an angular position (A) of the gap (δ) formed onone of at least one pair of neighboring tracks (112 a, 112 b) of thetracks (112) with respect to the center of rotation (center of 10) isdifferent from an angular position (B) of the gap (δ) formed in theother (112 b) of the neighboring tracks with respect to the center ofrotation (center of 10).

According to the arrangements of <4A> and <4B>, in a one-sided,two-recording layer type information storage medium on which informationcan be read from a plurality of recording layers from one surface side,even when the already recorded portion and non-recorded portion have alight reflectance difference, inter-layer crosstalk due to the influenceof the presence/absence of recording marks on the other recording layercan be greatly reduced, and high reliability of a reproduction signalcan be assured.

<5A> An information storage medium which is a recordable informationmedium (9) on which data recording is continuously done to form apredetermined gap (δ) between neighboring predetermined recording units(ECC blocks) along tracks (112), characterized in that a mark (141; aunique pattern which repeats itself a plurality of number of times atτ+2τ); a kind of address pattern) which indicates a recording startposition for the continuous data recording for respective predeterminedrecording units (ECC blocks) is pre-recorded by wobble modulation of thetracks (112).

According to the arrangement of <5A>, the following effects (A) to (C)are obtained:

A) Since the mark indicating the recording start position for continuousdata recording is present along the tracks on the information storagemedium, and the recording start position can be set using that mark, therecording position on the information storage medium can be accuratelydetermined.

B) Since the recording start position can be accurately set by effect(A), length δ of each gap region can be reduced. As a result, therecording capacity (recording efficiency) of the information storagemedium can be improved.

In other words, when length δ of each gap region is reduced, and therecording start position precision is low, rewrite data may be partiallyoverwritten on already recorded data (may destroy already recorded data)before and after data to be rewritten upon writing for respectivecontinuous recording units. Since such problem can be avoided using theaforementioned mark, length δ of each gap region can be reduced.

C) When the mark indicating the recording start position is pre-recordedby wobble modulation, even when recording marks are recorded on the markindicating the recording start position, no influence of a wobblemodulation signal is superposed on a reproduction signal of theserecording marks (unlike in the conventional prepit type). Therefore,since recording marks can be recorded on the mark indicating therecording start position, the recording efficiency can be improved, andthe recording capacity of the information storage medium can beincreased.

<6A> An information recording method characterized in that theinformation storage medium of <5A> is used, and after a mark positionindicating a recording start position for continuous data recording isdetected (YES in step ST116), continuous recording is started.

<6B> An information recording apparatus characterized in that theinformation storage medium of <5A> is used, and after a mark positionindicating a recording start position for continuous data recording isdetected (YES in step ST116), continuous recording is started.

According to the arrangements of <6A> and <6B>, the following effects(D) to (F) are obtained:

D) Since the mark indicating the recording start position for continuousdata recording is present along the tracks on the information storagemedium, and the recording start position can be set using that mark, therecording position on the information storage medium can be accuratelydetermined.

E) Since the recording start position can be accurately set by effect(D), length δ of each gap region can be reduced. As a result, therecording capacity (recording efficiency) of the information storagemedium can be improved.

In other words, when length δ of each gap region is reduced, and therecording start position precision is low, rewrite data may be partiallyoverwritten on already recorded data (may destroy already recorded data)before and after data to be rewritten upon writing for respectivecontinuous recording units. Since such problem can be avoided using theaforementioned mark, length δ of each gap region can be reduced.

F) When the mark indicating the recording start position is pre-recordedby wobble modulation, even when recording marks are recorded on the markindicating the recording start position, no influence of a wobblemodulation signal is superposed on a reproduction signal of theserecording marks (unlike in the conventional prepit type). Therefore,since recording marks can be recorded on the mark indicating therecording start position, the recording efficiency can be improved, andthe recording capacity of the information storage medium can beincreased.

1. (canceled)
 2. An information storage medium comprising: at least onepair of neighboring tracks formed on the information storage mediumhaving a center of rotation, wherein said information storage medium isa one-sided, multilayer type optical disc, two layers of which arerespectively provided with said neighboring tracks, one of saidneighboring tracks is configured to record information of a combinationof first group recording units and a first non-data portion which islocated between the first group recording units, an other of saidneighboring tracks is configured to record information of a combinationof second group recording units and a second non-data portion which islocated between the second group recording units, an angular position ofthe first non-data portion with respect the center of rotation isdifferent from an angular position of the second non-data portion withrespect to the center of rotation, and a plurality of ECC blocks areformed on any of neighboring tracks such that one of the first andsecond non-data portions is formed after an end of one of the ECC blocksand before a start of a next one of the ECC blocks.
 3. An informationstorage medium comprising: at least two pairs of neighboring tracksformed on the information storage medium having a center of rotation,wherein one of said neighboring tracks is configured to recordinformation of a combination of first group recording units and a firstnon-data portion which is located between the first group recordingunits, an other of said neighboring tracks is configured to recordinformation of a combination of second group recording units and asecond non-data portion which is located between the second grouprecording units, and an angular position of the first non-data portionwith respect the center of rotation is different from an angularposition of the second non-data portion with respect to the center ofrotation.